1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method, and more particularly to a semiconductor device manufacturing method that includes a contact hole forming process.
2. Description of Related Art
In a semiconductor device that is manufactured by forming multiple films on a substrate, contact holes are usually formed to connect a wire in an upper layer with a wire or an electrode in a lower layer. These contact holes are usually constructed by forming a resist pattern on the upper layer using a lithography process and then performing an etching process until the lower layer is exposed.
However, the conventional semiconductor device manufacturing method has problems. For example, the resist pattern is occasionally displaced when it is formed, and a portion of the silicon oxide film of the device separation unit is occasionally removed when a silicon nitride film that is used as an etching stopper is over-etched. Given these problems, in order to prevent the device characteristics and the manufacturing yield from deteriorating, the structure of the semiconductor device is determined taking the margin of alignment into consideration.
As the semiconductor device is scaled down, the dimensions of the structure of the semiconductor device such as the width of the activation region between device separation regions, the width of the transfer gate, the size of the contact hole, and the like are being scaled down also. However, the margin of alignment is not being scaled down accordingly. Therefore, the margin of alignment is one of the major factors preventing a further scale reduction of the semiconductor device.